Defensive traits are hypothesized to benefit prey by reducing predation risk from a focal predator but come at a cost to the fitness of the prey. Variation in the expression of defensive traits is seen among individuals within the same population, and in the same individual in response to changes in the environment (i.e., phenotypically plastic responses). It is the relative magnitude of the cost and benefit of the defensive trait that underlies the defensive trait expression and its consequences to the community. However, whereas the cost has received much attention in ecological research, the benefit is seldom examined. Even in a defensive trait as extensively studied as vigilance, there are few studies of the purported benefit of the behavior, namely that vigilance enhances survival. We examined whether prey vigilance increased survival and quantified that benefit in a natural system, with white‐tailed deer (Odocoileus virginianus) experiencing unmanipulated levels of predation risk from Florida panther (Puma concolor coryi). Deer that spent more time vigilant (as measured by head position using camera trap data) had a higher probability of survival. Indeed, an individual deer that was vigilant 75% of the time was more than three times as likely to be killed by panthers over the course of a year than a deer that was vigilant 95% of the time. Our results therefore show that within‐population variation in the expression of a defensive trait has profound consequences for the benefit it confers. Our results provide empirical evidence supporting a long‐held but seldom‐tested hypothesis, that vigilance is a behavior that reduces the probability of predation and quantifies the benefit of this defensive trait. Our work furthers an understanding of the net effects of a trait on prey fitness and predator–prey interactions, within‐population variation in traits, and predation risk effects.

中文翻译：

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衡量防御性特征的好处：警惕性和生存概率


防御性特征被假设通过降低焦点捕食者的捕食风险来使猎物受益，但以牺牲猎物的健康状况为代价。防御性状表达的差异可见于同一种群内的个体之间，以及同一个体对环境变化的反应（即，表型可塑性反应）。防御性特征的成本和收益的相对大小是防御性特征表达及其对社区的影响的基础。然而，尽管成本在生态研究中受到了很多关注，但其好处却很少被研究。即使在像警惕这样被广泛研究的防御性特征中，也很少有关于这种行为的所谓好处的研究，即警惕可以提高生存率。我们研究了猎物警惕性是否能提高生存率，并量化了自然系统中的益处，白尾鹿 （Odocoileus virginianus） 经历了佛罗里达黑豹 （Puma concolor coryi） 不受控制的捕食风险水平。花更多时间警惕的鹿（使用相机陷阱数据通过头部位置测量）的生存概率更高。事实上，一头 75% 时间保持警惕的鹿在一年内被黑豹杀死的可能性是一头 95% 时间保持警惕的鹿的三倍多。因此，我们的结果表明，防御性特征表达的种群内变异对其带来的好处具有深远的影响。我们的结果提供了实证证据，支持一个长期存在但很少经过检验的假设，即警惕是一种降低捕食可能性并量化这种防御性特征的好处的行为。 我们的工作进一步了解了性状对猎物适应性和捕食者-猎物相互作用、种群内性状变异和捕食风险影响的净影响。